In typical flow cytometry systems, the fluidics system functions to draw sample particles into a sample stream and transport the sample stream through an interrogation zone. The fluidics system typically uses a pressurized sheath stream to hydrodynamically focus the sample stream, which is known as the core stream, within the center of the sheath stream. The process of hydrodynamic focusing (also known as coaxial flow) results in laminar flow under preferred conditions and enables the optical system of the flow cytometer to illuminate, and thus analyze, the sample particles with uniformity and repeatability. Ideally, the particles within the core stream are positioned in the center of the interrogation zone. For many applications, particles are ideally arranged in a “single file” line within the core stream, although for other applications the ideal core stream may have a different arrangement of particles. For instance, one common problem in flow cytometry is the necessity for coincident detection of multiple particles known generally as “aggregate particles” that are closely spaced or joined in the sample. Depending on the experiment, closely spaced aggregate particles can either be undesirable (compromising data such as by causing ambiguity regarding which particle an input signal is for) or desirable (such as cells in the process of cell division/mitosis). To accomplish a particular particle arrangement across multiple sample particle sizes, the core stream is typically adjusted in an open loop manner by multiple controls that alter (1) the pressure of the sample line, (2) the pressure of the sheath line, and (3) the sample-to-sheath pressure differential. Most commonly, at least two of the three settings will need to be adjusted in the course of setting the core stream size.
Adjusting the multitude of controls used to set the core stream, including the sample flow rate (i.e. sample line pressure), sheath flow rate (i.e. sheath line pressure), and sample-to-sheath pressure differential often requires multiple iterations of adjustments. Setting the multiple control flow cytometer core stream controls can be challenging to, and time consuming for, the experienced user, and can lead to inaccurate data (i.e. event) collection and suboptimal core stream formation in the hands of an inexperienced user. Furthermore, a substantial amount of sample must be consumed in order to set the pressure settings, which is a further disadvantage of the present system particularly when the sample to be analyzed is available in a very limited quantity.
Thus, there is a need in the flow cytometer field to create a new, improved, and useful fluidic system that avoids or minimizes these disadvantages. This invention provides such a new, improved, and useful detection and fluidic system for a flow cytometer.